So far these lower animals are concerned, they are given, being given intelligence how to eat, how to sleep, how to mate, how to defend. But a human being, if he engages himself in the service of the Lord, then Lord will give intelligence how to come back to home, back to Godhead.

This is stated in the Bhagavad-gītā. That is the condition. Teṣāṁ satata-yuktānāṁ bhajatāṁ prīti-pūrvakam [Bg. 10.10]. "Only to those who are engaged in devotional service with love and faith, I give him intelligence how to come back to home, back to Godhead." Therefore, after coming to human form of body, we must awaken our intelligence about understanding the Supreme Lord. And if we take up the process sincerely, with love, then Lord within will give you dictation: "You come this way, come this way, come this way." Otherwise, not." -Srila Prabhupada Morning Walk—April 20, 1973, Los Angeles